Well, it's because of how people see Bitcoin right now.
They see it more like a hedging tool towards the inflation.
They see it as an asset more than a currency.

They see it as a tool for them to be rich hence, they're storing it because they believe that in a few years, their holding will be worth 2x or 3x or even more, and I can't blame them because that's what history price of Bitcoin is showing to us. I don't want to pinpoint a particular investor, but we can't blame the fact that many thinks Bitcoin more than an asset than a currency because of the fact that it is speculative, and like I said, many thinks that it will go up in a few years if they will just hold their token so why would they spend it if they can just hold it for a long time, and become rich.

Let's not also forget the fact that not all countries are accepting Bitcoin as another mode of payment (if you're pertaining about Bitcoin being used as a currency OFC). I just don't know why you said that storing Bitcoin = pyramid scheme. Maybe elaborate it?